JP2005171316A - Raw material powder for sintered compact target for forming optical recording medium protective film, method of producing sintered compact target using the powder, and sintered compact target - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide raw material powder for a sintered compact target in which ZnS powder and SiO<SB>2</SB>powder are uniformly mixed without unevenness of density, to provide a method of producing a target where productive efficiency is improved, and further, a sintered compact target having a uniform structure, free of the unevenness of density, and having high relative density can be obtained, and to provide the target. <P>SOLUTION: The raw material powder for a sintered compact target for forming a optical recording medium protective film is obtained by improving raw material powder having a composition composed of SiO<SB>2</SB>powder with a mean particle diameter of 0.0005 to 10 μm by 10 to 30 mol%, and the balance ZnS powder with a mean particle diameter of 1 to 20 μm, and in which the SiO<SB>2</SB>powder is dispersed into the ZnS matrix, and is characterized in that it contains straight chain alkylcarboxylic acid by 0.1 to 5 wt.% to the mixture. Further, the raw material powder is charged inside a hot press die, and is hot-pressed at 700 to 1,200°C under 20 to 40 MPa in a vacuum or in a gaseous Ar atmosphere, thus the sintered compact target is produced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an optical recording medium protective film comprising a zinc sulfide (ZnS) -silicon dioxide (SiO ₂ ) sintered body for forming a protective film such as a phase change optical disk for recording and erasing information using a laser. The present invention relates to a raw material powder of a forming sintered body target, a method for producing a sintered body target using the powder, and a sintered body target.

A ZnS-SiO ₂ film in which SiO ₂ is dispersed and mixed in ZnS is used as a protective film for a phase change optical disk or the like that records and erases information using a laser. As a sputtering target for forming this ZnS—SiO ₂ film, it consists of a homogeneous hybrid solidified body of high-purity ZnS having a purity of 99.999% by weight or more and high-purity SiO ₂ having a purity of 99.999% by weight or more, A sputtering target having a relative density of at least% has been proposed (see, for example, Patent Document 1). In addition to improving the film formation rate and stable film formation characteristics with the target shown in Patent Document 1, it is possible to improve productivity and have industrially useful effects.

However, since the above-mentioned conventional target is composed of a sintered body made of raw material powder using SiO ₂ having a large particle size, charges are generated on the coarse particles of SiO ₂ existing on the surface of the sputtering surface of the target during sputtering. Since it is easy to concentrate, there is a problem that abnormal discharge or the like is likely to occur, and as a result, particles are generated.
As a measure for solving such problems, a sputtering target composed of a sintered body mainly composed of ZnS and SiO ₂ has been proposed in which the particle size of SiO ₂ in the sintered body is 30 μm or less. (For example, refer to Patent Document 2). The target disclosed in Patent Document 2 hardly causes abnormal discharge during sputtering, can prevent generation of particles, and enables stable sputtering.

On the other hand, the present applicant, as a sputtering target for forming an optical recording protective film that hardly generates cracks even when performing high-power sputtering, has an average particle diameter in the range of 10 to 30 μm and a specific surface area value in a ZnS substrate. Has proposed a sputtering target having a structure in which SiO ₂ grains in a range of 0.5 to 5.0 m ² / g are uniformly dispersed (see, for example, Patent Document 3). Even if high power sputtering is performed with the target shown in Patent Document 3, it is difficult to generate cracks, so that a protective film such as a phase-change optical disk can be formed more efficiently than in the prior art. Cost reduction can be performed.
Further, the applicant, as a target capable of forming an optical recording protective film having a uniform thickness over a large area, SiO _2: containing 10 to 30 mol%, a sintered body having a composition balance being ZnS As a sputtering target, ZnS has proposed a sputtering target in which the phase ratio (α / β) of α-type crystal and β-type crystal is in the range of 0 ≦ α / β <0.0005 (see, for example, Patent Document 4). . With the target shown in Patent Document 4, an optical recording protective film having a uniform film thickness can be obtained over a wide range even when high-power sputtering is performed.
JP-A-6-65725 (Claim 1, paragraph [0021]) JP 11-350119 A (Claim 1, paragraph [0030]) JP 11-350121 A (Claim 1, paragraph [0015]) JP 2000-297362 A (Claim 1, paragraph [0018])

  However, in each of the targets shown in Patent Documents 1 to 4, the flowability of the mixed powder ZnS powder produced before target production was poor, and the uniformity of the mixed powder was not sufficiently obtained. If the mixed powder does not have sufficient uniformity, it is difficult to uniformly fill the hot press mold, and the sintered compact target after firing tends to have uneven density and low relative density. It was.

An object of the present invention is to provide a raw material powder for a sintered body target for forming an optical recording medium protective film, in which ZnS powder and SiO ₂ powder are uniformly mixed without unevenness in density.
Another object of the present invention is to provide a sintered body target manufacturing method and a sintered body target in which a production target is improved and a sintered body target having a uniform structure, no density unevenness, and a high relative density is obtained. Is to provide.

The invention according to claim 1 has a composition comprising 10 to 30 mol% of SiO ₂ powder having an average particle diameter of 0.0005 to 10 μm, and the remainder comprising ZnS powder having an average particle diameter of 1 to 20 μm, This is an improvement of a raw material powder for a sintered body target for forming an optical recording medium protective film in which SiO ₂ powder is dispersed.
The characteristic structure exists in the place which contains 0.1 to 5 weight% of linear alkylcarboxylic acid with respect to a mixture.
In the raw material powder according to claim 1, by containing 0.1% to 5% by weight of linear alkyl carboxylic acids, the fluidity of the ZnS powder and SiO ₂ powder is improved, respectively, ZnS powder and SiO ₂ powder Mix uniformly without uneven density.

The invention according to claim 2 is the invention according to claim 1, wherein the linear alkylcarboxylic acid is a raw material powder containing at least one of stearic acid or zinc stearate.
The invention according to claim 3 is the invention according to claim 1, and is a raw material powder in which a linear alkylcarboxylic acid is attached to either or both of the ZnS powder surface and the SiO ₂ powder surface.
In the raw material powder according to claim 3, the flowability of the ZnS powder and the SiO ₂ powder in the raw material powder is obtained by adhering the linear alkylcarboxylic acid to either or both of the ZnS powder surface and the SiO ₂ powder surface. Each improves.

The invention according to claim 4 is a method in which the raw material powder according to any one of claims 1 to 3 is filled in a hot press mold and a pressure of 20 to 40 MPa at a temperature of 700 to 1200 ° C. in a vacuum or an Ar gas atmosphere. Is a method of manufacturing a sintered compact target for forming an optical recording medium protective film by hot pressing.
In the method according to claim 4, when the sintered compact target is manufactured, the filling density in the hot press mold is increased by using the raw material powder having improved fluidity, and the hot press mold is easily filled. Therefore, the production efficiency in the target hot pressing process is improved. Moreover, by using the raw material powder having improved fluidity, a sintered compact target having a uniform structure, no density unevenness, and a high relative density can be obtained.

The invention according to claim 5 is a sintered compact target for forming an optical recording medium protective film obtained by the method according to claim 4.
In the sintered compact target according to the fifth aspect, since the raw material powder with improved fluidity is used, the structure is uniform, the density is not uneven, and the relative density is high.

The invention according to claim 6 is an optical recording medium protective film formed using the sintered compact target according to claim 5.
The invention according to claim 7 is an optical recording medium having the protective film according to claim 6.

In the raw material powder of the sintered body target for forming an optical recording medium protective film of the present invention, the flowability of the ZnS powder and the SiO ₂ powder is increased by containing 0.1 wt% to 5 wt% of the linear alkylcarboxylic acid. In order to improve, the ZnS powder and the SiO ₂ powder are mixed uniformly without uneven density. Moreover, in the manufacturing method of the sintered compact target of this invention, and a sintered compact target, when manufacturing a sintered compact target, the filling density in a hot press type | mold is used by using the raw material powder which improved fluidity | liquidity. As it increases, filling into the hot press mold becomes easy, so that the production efficiency in the hot press process of the target is improved. Moreover, by using the raw material powder having improved fluidity, a sintered compact target having a uniform structure, no density unevenness, and a high relative density can be obtained. Since the relative density is high, the bending strength is high even when a large sintered compact target is molded, and even when high-power sputtering is performed, spatter cracks do not occur, so a protective film such as a phase change optical disk is efficiently formed. be able to.

Next, the best mode for carrying out the present invention will be described.
The raw material powder for producing the sintered body target for forming an optical recording medium protective film of the present invention contains 10 to 30 mol% of SiO ₂ powder having an average particle diameter of 0.0005 to 10 μm, and the rest is the average particle diameter. It is a raw material powder having a composition comprising 1 to 20 μm of ZnS powder, in which SiO ₂ powder is dispersed in the ZnS matrix. The characteristic structure exists in the place which contains 0.1 to 5 weight% of linear alkylcarboxylic acid with respect to a mixture.
This raw material powder, by containing 0.1% to 5% by weight of linear alkyl carboxylic acids, the fluidity of the ZnS powder and SiO ₂ powder is improved, respectively, ZnS powder and SiO ₂ powder density unevenness of Mix evenly. The reason why the content of the linear alkylcarboxylic acid is defined as 0.1% by weight to 5% by weight is that sufficient fluidity cannot be obtained when the content is less than 0.1% by weight. This is because the sintered compact target using the raw material powder exceeding 5% by weight has a large amount of impurities derived from the linear alkyl carboxylic acid and causes a problem that both the relative density and the bending strength are lowered. The preferred content is 0.2% to 1% by weight. As linear alkylcarboxylic acid, what contains at least 1 sort (s) of a stearic acid or a zinc stearate is suitable. The flowability of the ZnS powder and the SiO ₂ powder in the raw material powder is improved by attaching the linear alkylcarboxylic acid to either or both of the ZnS powder surface and the SiO ₂ powder surface.

The average particle size of the SiO ₂ powder is defined within a range of 0.0005 to 10 μm. The defining the SiO ₂ powder to the average particle diameter 0.0005~10μm have an average particle diameter is because it is difficult to produce a powder of less than 0.0005, the SiO ₂ powder having an average particle diameter exceeds 10μm This is because, when the target used is sputtered, electric charges tend to concentrate on the coarse SiO ₂ particles existing on the surface of the target sputtering surface during sputtering, and abnormal discharge or the like is likely to occur, resulting in generation of particles. A preferable average particle diameter of the SiO ₂ powder is 0.01 to 5 μm. The average particle size of the ZnS powder is defined within a range of 1 to 20 μm. The reason why the ZnS powder is defined to have an average particle size of 1 to 20 μm is that if the average particle size is less than 1 μm, the relative density of the fired target is reduced, and if the average particle size exceeds 20 μm, SiO ₂ This is because it is difficult to uniformly disperse ZnS and ZnS, and the SiO ₂ phase of the fired target causes a large defect. The preferable average particle diameter of the ZnS powder is 2 to 10 μm. Both the ZnS powder and the SiO ₂ powder have a purity of 99.999% by weight or more. A preferred composition contains 15 to 25 mol% of SiO ₂ powder and the remainder is ZnS, and particularly preferably contains 20 mol% of SiO ₂ powder and the remainder is composed of ZnS.

Next, a method for producing a sintered compact target for forming an optical recording medium protective film will be described.
First, a commercially available ZnS powder having a purity of 99.999% by weight or more is prepared. This commercially available ZnS powder is subjected to a heat treatment in an Ar gas atmosphere at a temperature of 300 to 700 ° C. for 0.5 to 12 hours to remove impurity gases such as H ₂ S that are contained in the commercially available ZnS powder, A ZnS powder for a sintered compact target of 20 μm is prepared. The average particle diameter of the SiO ₂ powder 0.0005～10Myuemu, prepared respectively a straight-chain alkyl carboxylic acids containing at least one stearic acid or zinc stearate. Next, the SiO ₂ powder, the ZnS powder, and the linear alkylcarboxylic acid are mixed so that the composition ratio is 10 to 30 mol%: 89.5 to 65 mol%: 0.5 to 5 mol%. Put together with φ2 mm alumina balls in a polypot and dry mix for 0.5 to 3 hours to produce a sintered target powder. By this dry mixing, the linear alkylcarboxylic acid is attached to either or both of the ZnS powder surface and the SiO ₂ powder surface, and the fluidity of the ZnS powder and the SiO ₂ powder in the raw material powder is improved. As a result, the ZnS powder and the SiO ₂ powder are uniformly mixed without density unevenness. The produced raw material powder is filled in a graphite hot press mold. Next, the raw powder is hot pressed by holding a hot press mold filled with the raw material powder in an Ar gas atmosphere at a temperature of 700 to 1200 ° C. and a pressure of 20 to 40 MPa for 1 to 20 hours, followed by a cooling rate of 60 A hot press body is produced by cooling at ~ 180 ° C / hour. It is preferable to hot-press the mixed powder by holding it at a temperature of 850 to 1150 ° C. and a pressure of 25 to 35 MPa for 2 to 8 hours, followed by cooling at a cooling rate of 120 to 180 ° C./hour. A sintered compact target is obtained by machining the obtained hot press body to a predetermined diameter and a predetermined thickness. When the sintered compact target is manufactured by the above method, the filling density into the hot press mold is increased by using the raw material powder having improved fluidity, and the filling into the hot press mold is facilitated. Production efficiency in the target hot pressing process is improved. Moreover, by using the raw material powder having improved fluidity, a sintered compact target having a uniform structure, no density unevenness, and a high relative density can be obtained.

Next, examples of the present invention will be described in detail together with comparative examples.
<Example 1>
First, a commercially available ZnS powder having a purity of 99.999% by weight or more was prepared. This commercially available ZnS powder was heat-treated in an Ar gas atmosphere at a temperature of 650 ° C. for 1 hour to remove impurity gases such as H ₂ S contained in the commercially available ZnS powder in a large amount, thereby producing a ZnS powder for a sintered compact target. The average particle size of the produced ZnS powder for a sintered compact target was about 8 μm. Next, SiO ₂ powder having an average particle size of 1.0 μm and a purity of 99.999% by weight was prepared. Moreover, powdered stearic acid (manufactured by Kanto Chemical Co., Inc .; special grade) was prepared as a linear alkylcarboxylic acid.
Next, the composition ratio of the ZnS powder, the first SiO ₂ particles, and the linear alkyl carboxylic acid is mixed at 80: 19: 1, and this mixed powder is put into a polypot together with φ2 mm alumina balls for 1 hour. Dry mixing was performed to prepare a raw material powder for a sintered compact target. The produced raw material powder was filled in a hot press die made of graphite. Next, the raw powder is hot-pressed by holding a hot press mold filled with the raw powder in an Ar gas atmosphere at a pressure of 24.5 MPa (250 kgf / cm ² ) and a temperature of 1000 ° C. for 2 hours, followed by a cooling rate. A hot press body was produced by cooling at 120 ° C./hour. The obtained hot press body was machined into dimensions of 200 mm in diameter and 5 mm in thickness to produce a disk-shaped sintered body target.

<Example 2>
A ZnS powder for a sintered body target, an SiO ₂ powder and powdered stearic acid used in Example 1 were prepared. First, the composition ratio of ZnS powder and stearic acid was mixed to be 80: 1, and this mixed powder was put in a polypot together with alumina balls having a diameter of 2 mm and dry-mixed for 1 hour. After 1 hour sampling and SEM observation, it was confirmed that stearic acid was coated on the ZnS powder surface. Subsequently, the SiO ₂ powder was put in a polypot so that the composition ratio of ZnS powder, SiO ₂ powder, and stearic acid was 80: 19: 1, and was dry-mixed for 20 minutes to produce a raw material powder for a sintered compact target. A sintered compact target was produced in the same manner as in Example 1 using the produced raw material powder.
<Example 3>
A ZnS powder for a sintered body target, an SiO ₂ powder and powdered stearic acid used in Example 1 were prepared. First, the composition ratio of SiO ₂ powder and stearic acid was mixed so as to be 19: 1, and this mixed powder was put into a polypot together with alumina balls of φ2 mm and dry-mixed for 1 hour. After 1 hour of sampling and SEM observation, it was confirmed that stearic acid was coated on the SiO ₂ powder surface. Subsequently, the ZnS powder was put in a polypot so that the composition ratio of ZnS powder, SiO ₂ powder and stearic acid was 80: 19: 1 and dry-mixed for 20 minutes to produce a sintered body target raw material powder. A sintered compact target was produced in the same manner as in Example 1 using the produced raw material powder.

<Example 4>
A sintered compact target was produced in the same manner as in Example 1 except that the composition ratio of ZnS powder, SiO ₂ powder and stearic acid was 82: 14: 4.
<Example 5>
A sintered compact target was produced in the same manner as in Example 1 except that the composition ratio of ZnS powder, SiO ₂ powder and stearic acid was 75: 24.5: 0.5.
<Example 6>
Example except that ZnS powder having an average particle size of 4 μm and SiO ₂ powder having an average particle size of 2.0 μm were used, respectively, and the composition ratio of ZnS powder, SiO ₂ powder and stearic acid was 80: 18.5: 1.5. In the same manner as in Example 1, a sintered compact target was produced.
<Example 7>
A sintered compact target was produced in the same manner as in Example 1 except that zinc stearate was used as the linear alkylcarboxylic acid.
<Example 8>
A sintered compact target was prepared in the same manner as in Example 1 except that zinc stearate was used as the linear alkylcarboxylic acid and the composition ratio of ZnS powder, SiO ₂ powder and zinc stearate was 82: 14: 4.

<Comparative Example 1>
A sintered body target was produced in the same manner as in Example 1 except that the linear alkylcarboxylic acid was not used and the composition ratio of the ZnS powder and the SiO ₂ powder was 80:20.
<Comparative example 2>
A sintered compact target was produced in the same manner as in Example 1 except that the composition ratio of ZnS powder, SiO ₂ powder and stearic acid was 75:15:10.
<Comparative Example 3>
Example except that ZnS powder having an average particle size of 4 μm and SiO ₂ powder having an average particle size of 2.0 μm were used, respectively, and the composition ratio of ZnS powder, SiO ₂ powder and stearic acid was 80: 19.95: 0.05. In the same manner as in Example 1, a sintered compact target was produced.
<Comparative example 4>
A sintered compact target was prepared in the same manner as in Example 1 except that zinc stearate was used as the linear alkylcarboxylic acid and the composition ratio of ZnS powder, SiO ₂ powder and zinc stearate was 75:15:10.

<Comparison test 1>
First, the angle of repose of the raw material powder for sintered compact target produced in Examples 1 to 8 and Comparative Examples 1 to 4 was measured. Subsequently, 100 sintered bodies of Examples 1 to 8 and Comparative Examples 1 to 4 were fired one by one, and the cracks and obvious density and color unevenness of the target immediately after firing were judged visually, and such a defective portion The number of targets having a count was counted as the firing failure rate. Next, the bending strength and relative density in the sintered compact targets of Examples 1 to 8 and Comparative Examples 1 to 4 were measured. Next, the sintered compact targets of Examples 1 to 8 and Comparative Examples 1 to 4 were each soldered to a molybdenum cooling backing plate with an iridium brazing material having a purity of 99.999% by weight, and this was subjected to high frequency magnetron sputtering. Sputtering gas Ar, sputtering gas pressure 0.665 Pa (5 × 10 ⁻³ Torr), sputtering power 13.56 MHz high frequency power 1500 kW (about 8.5 W / cm ² ), sputtering time 5 minutes Then, a protective film was formed on a Si substrate on which a 100 nm thick SiO ₂ film was laminated. Good sputtering characteristics were obtained for the sintered compact targets of Examples 1 to 8. On the other hand, in the sintered compact targets of Comparative Examples 1 to 4, the sputtering atmosphere was deteriorated by the gas released during sputtering, the film formation became unstable, and good reproducibility was not obtained. Next, sputtering was continuously performed under the above sputtering conditions, and it was visually observed whether sputter cracks occurred in the target. Table 2 shows the angle of repose, firing failure rate, relative density, bending strength, and presence / absence of spatter cracks in the sintered compact targets of Examples 1 to 8 and Comparative Examples 1 to 4, respectively.

As is clear from Table 2, the relative strengths of the targets of Comparative Examples 1 and 3 remained at 91%, and spatter cracks were also generated. This is probably because the hot press mold was not sufficiently filled in the production of the target. Further, in the targets of Comparative Examples 2 and 4, both the relative density and the bending strength were low, and spatter cracks were also generated. On the other hand, in the targets of Examples 1 to 8, it was found that the relative density and bending strength were high, the firing failure rate was low, and spatter cracking did not occur even when high-power high-frequency magnetron sputtering was performed.

Claims (7)

Average particle diameter contained 10 to 30 mol% of SiO ₂ powder 0.0005～10Myuemu, has a composition balance being ZnS powder having an average particle diameter of 1 to 20 [mu] m, SiO ₂ powder is dispersed in the ZnS matrix It is a raw material powder of a sintered body target for forming an optical recording medium protective film,
A raw material powder for a sintered body target for forming a protective film for an optical recording medium, wherein the linear alkylcarboxylic acid is contained in an amount of 0.1 to 5% by weight based on the mixture.   The raw material powder according to claim 1, wherein the linear alkylcarboxylic acid contains at least one of stearic acid and zinc stearate. The raw material powder according to claim 1, wherein the linear alkylcarboxylic acid is attached to either or both of the ZnS powder surface and the SiO ₂ powder surface.   Optical recording by filling the raw material powder according to any one of claims 1 to 3 in a hot press mold and hot pressing at a temperature of 700 to 1200 ° C and a pressure of 20 to 40 MPa in a vacuum or an Ar gas atmosphere. A method for producing a sintered compact target for forming a medium protective film.   The sintered compact target for optical recording medium protective film formation obtained by the method of Claim 4.   An optical recording medium protective film formed using the sintered compact target according to claim 5. An optical recording medium having the protective film according to claim 6.